Author: Andy Balaam

Continuing trying to get the simplest bit of real code we could think of to work, we need to finish off less-than-or-equals, and also make let mut work. You can find the source code at codeberg.org/andybalaam/milk and more of my stuff at artificialwor…

We are repeating ourselves with the SyntaxTree and TypedSyntaxTree enums. I thought the solution would be too complex, but on reflection it’s fine, so let’s share that code. You can find the source code at codeberg.org/andybalaam/milk and more of my s…

I spent ages yesterday trying to figure out how to use Rust’s tracing library (and tracing-subscriber) for a very simple logging use-case. I wanted to use tracing because a) it’s rapidly becoming standard everywhere and b) I was using libraries that us…

We realised last time that our type checker needs to move on from just saying “yes” or “no” for whether our program is OK: we need to keep hold of the type information we work out, so we can use it for error messages and possibly even within the evalua…

This is it: we’re going to do some actual type-checking. We want to be able to identify that let x: i32 = 3.0; is wrong, but for now we’re going to check some things that are right. Type-checking this kind of thing is way easier than the full type infe…

We want to have a go at some type-checking, so the first step is to write some code that causes a type error. We are going for let x: i32 = 3.0;. To do that, we need to be able to lex and parse the : i32 part… You can find the source code at codeber…

We have been putting up with a weird problem with our lexer: up to now it requires white space between each token. But, last time we created a backtracking iterator that we can use to fix this problem, so let’s go ahead and do it. You can find the sou…

Our parser kinda works, but it needs some work to be less terrible. We’ve realised we did a few things in awkward or wrong ways, so let’s fix them before they get out of hand. You can find the source code at codeberg.org/andybalaam/milk and more of my…

After lots of conversations with Element colleagues about message order in Matrix, and lots of surprises for me, I wanted to write down what I had learned before I forgot, and also write down some principles I think we should try to follow. A lot of th…

Refactoring our lexer, so all the awful things we did to make the tests pass are behind us. You can find the source code at codeberg.org/andybalaam/milk and more of my stuff at artificialworlds.net

Introducing my new series: writing a little Rust-like language in Rust. It will be an interpreted language, and (for now at least) it will try to work as much like real Rust as possible. Maybe one day it will be a useful language, but for now it’s pure…

Introducing my new series: writing a little Rust-like language in Rust. It will be an interpreted language, and (for now at least) it will try to work as much like real Rust as possible. Maybe one day it will be a useful language, but for now it’s pure…

Creating a custom Python extension in Rust. Series: Language basics, More syntax, Traits and generics, Building applications, Concurrency and parallelism, Trait objects, Async, Unsafe, FFI This section (FFI): 49: FFI, 50: Exercise 1, 51: Exercise 2, 5…

Using cargo-bindgen to generate bindings, automating what we need to do to use existing C code inside a Rust project. Series: Language basics, More syntax, Traits and generics, Building applications, Concurrency and parallelism, Trait objects, Async, …

Trying out calling Rust code from with a C program (should help with calling Rust from any compiled-to-native language too). Series: Language basics, More syntax, Traits and generics, Building applications, Concurrency and parallelism, Trait objects, …

Calling C code from Rust, Rust code from C-family languages, using cargo-bindgen, and creating Python extensions. Series: Language basics, More syntax, Traits and generics, Building applications, Concurrency and parallelism, Trait objects, Async, Unsa…

Calling C code from Rust, Rust code from C-family languages, using cargo-bindgen, and creating Python extensions. Series: Language basics, More syntax, Traits and generics, Building applications, Concurrency and parallelism, Trait objects, Async, Unsa…

As you may have noticed, I recently upgraded my blog from WordPress to Zola. This means that my home computer does the work of rendering the pages to HTML once, and my web server only has to provide the rendered HTML to your browser. This should mean t…

Implementing our own Result type that has a specific memory layout, so it can be used by Roc code. Series: Language basics, More syntax, Traits and generics, Building applications, Concurrency and parallelism, Trait objects, Async, Unsafe This section…

This is an early warning: I am actively working to move this blog away from WordPress, to a static site created using Zola. I am planning to keep as many URLs working as humanly possible, and the RSS feed URL should be unchanged. (With any luck, the pe…

Coding up a linked list based on raw pointers in Rust. Series: Language basics, More syntax, Traits and generics, Building applications, Concurrency and parallelism, Trait objects, Async, Unsafe This section (Async): 42: Why unsafe?, 43: Meaning of un…

Looking through some of the types of code you will be working with if you’re doing unsafe Rust, and some of the unsafe types you might want to use. Series: Language basics, More syntax, Traits and generics, Building applications, Concurrency and paral…

If you write unsafe Rust, you need to reason about “undefined behaviour”. We talk through what that means, and try to develop an intuition about why we can’t predict how our program will behave if we don’t follow the rules. Series: Language basics, Mo…

The unsafe keyword in Rust means two things: “You must read the docs!” or “I promise I read the docs and followed the rules!”. Series: Language basics, More syntax, Traits and generics, Building applications, Concurrency and parallelism, Trait objects…

There is a special mode in Rust programs called unsafe – why do we need it? Series: Language basics, More syntax, Traits and generics, Building applications, Concurrency and parallelism, Trait objects, Async, Unsafe This section (Async): 42: Why unsaf…

Writing a mini client to connect to our async Rust chat server. Series: Language basics, More syntax, Traits and generics, Building applications, Concurrency and parallelism, Trait objects, Async, Unsafe This section (Async): 34: What is async?, 35: F…

Writing a little chat server in async Rust. Series: Language basics, More syntax, Traits and generics, Building applications, Concurrency and parallelism, Trait objects, Async, Unsafe This section (Async): 34: What is async?, 35: Futures, 36: async/aw…

Writing a one-shot queue using async Rust, this time with a little less help. Series: Language basics, More syntax, Traits and generics, Building applications, Concurrency and parallelism, Trait objects, Async, Unsafe This section (Async): 34: What is…

Writing our own multi-producer-single-consumer (MPSC) queue using async Rust. Series: Language basics, More syntax, Traits and generics, Building applications, Concurrency and parallelism, Trait objects, Async, Unsafe This section (Async): 34: What is…

We talked about how Futures have poll methods, but who calls them? That is the job of the runtime. We talk about how to launch your async code and how to choose the right runtime, and then we have a very brief look at some Web frameworks that are based…

Attempting to explain as slowly as possible what actually happens when the compiler finds an async function containing awaits: it writes a poll method for you to create something that implements Future. The generated poll method polls the Futures you a…

Exploring what a Future is in async Rust and how we could manually write code that polls futures. Normally, we avoid this manual work by using the async and await keywords, but looking into this helps us understand what those keywords really do. Serie…

What async programming is and what it looks like in Rust. Series: Language basics, More syntax, Traits and generics, Building applications, Concurrency and parallelism, Trait objects, Async, Unsafe This section (Async): 34: What is async?, 35: Futures…

Following through an exercise using a trait object with dynamic dispatch to choose different behaviour at runtime. Series: Language basics, More syntax, Traits and generics, Building applications, Concurrency and parallelism, Trait objects, Async, Uns…

I am really excited to say I was elected to the Governing Board of the Matrix Foundation! I was really surprised because there were lots of people standing, and the quality of the candidates was very high, but I am one of the lucky ones. I hope I can d…

Trying out the typestate pattern by tracking the state of a 3D printer by changing our type instead of updating a variable whenever it changes. Series: Language basics, More syntax, Traits and generics, Building applications, Concurrency and paralleli…

Some good patterns to follow in your code e.g. “newtype”, “typestate” and one to avoid. Series: Language basics, More syntax, Traits and generics, Building applications, Concurrency and parallelism, Trait objects, Async, Unsafe This section (Trait obj…

Some good patterns to follow in your code e.g. “newtype”, “typestate” and one to avoid. Series: Language basics, More syntax, Traits and generics, Building applications, Concurrency and parallelism, Trait objects, Async, Unsafe This section (Trait obj…

Trying to explain why the rules for object safety are the way they are, and how to create and use a trait objects. Series: Language basics, More syntax, Traits and generics, Building applications, Concurrency and parallelism, Trait objects, Async, Uns…

Explaining how to hold on to something even when we don’t know its exact type, just what trait it implements. Series: Language basics, More syntax, Traits and generics, Building applications, Concurrency and parallelism, Trait objects, Async, Unsafe T…

Huge thanks to Micah Scott for hosting my videos on diode.zone until recently. My videos are moving to video.infosec.exchange/a/andybalaam – please update all your feeds. (Thanks to Jerry Bell for running that – please donate!) You can follow this blog…

I received a very kind email today from someone who had found my page Resources for year 6 teachers on coding and programming helpful, and wanted to suggest another link for me to add, about AI resources. I’m sure it was a helpful and useful link, but …

Implementing a simplified form of Mutex. Series: Language basics, More syntax, Traits and generics, Building applications, Concurrency and parallelism, Trait objects, Async, Unsafe This section (Concurrency and parallelism): 24: Parallelism, 25: Threa…

Searching across multiple documents in parallel with Rayon. Series: Language basics, More syntax, Traits and generics, Building applications, Concurrency and parallelism, Trait objects, Async, Unsafe This section (Concurrency and parallelism): 24: Par…

Update: I just discussed this with my son and I really want to emphasise: It does make a difference who is in power. The previous Labour government significantly improved primary education and many other public services. Don’t lose hope! Here are the c…

How to spawn threads and deal with lifetimes, how to send or share state across threads, and what Send and Sync mean. Series: Language basics, More syntax, Traits and generics, Building applications, Concurrency and parallelism, Trait objects, Async, …

What concurrency and parallelism are, a brief intro to Rayon, and a quick note on closures. Series: Language basics, More syntax, Traits and generics, Building applications, Concurrency and parallelism, Trait objects, Async, Unsafe This section (Concu…

Testing, benchmarking and optimising a small program that plays FizzBuzz. Series: Language basics, More syntax, Traits and generics, Building applications, Concurrency and parallelism, Trait objects, Async, Unsafe This section (Building applications):…

Building a command-line quiz application to bed in our knowledge about crates, modules and serialisation. All done using test-driven development. Series: Language basics, More syntax, Traits and generics, Building applications, Concurrency and paralle…

Going through an exercise on serialization with serde. Series: Language basics, More syntax, Traits and generics, Building applications, Concurrency and parallelism, Trait objects, Async, Unsafe This section (Building applications): 18: Dependencies, …

How to write unit tests in your Rust code, and some quick pointers on writing integration and benchmark tests. Series: Language basics, More syntax, Traits and generics, Building applications, Concurrency and parallelism, Trait objects, Async, Unsafe …

I have decided to stand for election to the Matrix Governing Board, which is a brand new body which advises and oversees the work of the Matrix Foundation. I will stand as an Individual Member, not representing a company or project. Contents: Purpose …

Tips and rules for writing good APIs that are easy for other people to use. Try to make them Unsurprising, Flexible, and Obvious. Series: Language basics, More syntax, Traits and generics, Building applications, Concurrency and parallelism, Trait obje…

How to describe details of your Rust project with a Cargo.toml file, and how to find and add dependencies (other people’s code). Series: Language basics, More syntax, Traits and generics, Building applications, Concurrency and parallelism, Trait objec…

Finishing off the exercises on Rust traits, designing a customised version of Vec. Series: Language basics, More syntax, Traits and generics, Building applications, Concurrency and parallelism, Trait objects, Async, Unsafe This section (Traits and gen…

DON’T DO THIS: the Signal app has the ability to make daily backups of your messages, and when you choose a folder to backup into, you can choose “Nextcloud” as the device, then choose a Nextcloud folder to back up to. Don’t do that. Although the above…

Going through some exercises on Rust traits, designing a customised version of Vec. Series: Language basics, More syntax, Traits and generics, Building applications, Concurrency and parallelism, Trait objects, Async, Unsafe This section (Traits and ge…

Rust has a feature where if you import two things from the same module you can abbreviate it like this: use mypkg::{MyStruct1, MyStruct2}; If you prefer, you can keep them separate, like this: use mypkg::MyStruct1; use mypkg::MyStruct2; I do prefer. St…

This time we tackle one of the most tricky areas for a new Rust programmer: lifetimes. The key point is that when we add lifetime bounds (‘a or similar) to a function signature, this is not to help Rust compile our function: it’s to help Rust understan…

A tour of some of the most interesting traits in the standard library including Add etc. to overload operators, Sized, Sync and Send for telling the compiler special things about your type, Clone and Copy for copying things, Into and From for convertin…

Following on from video 12, looking at how to add type information to traits, to make them flexible enough to describe generic code with different types, for example how to add a u32 to a u64 and return a u128, without defining a whole new trait for ev…

Explaining what a trait is, and how to use it. A trait is a bit like an Interface in Java or Go, or an Abstract Base Class in C++ or Python, but it can be used to define behaviour at compile-time as well as at run-time. We go through an example of why …

Going through some exercises on Rust ownership, references, slices and error handling. Series: Language basics, More syntax, Traits and generics, Building applications, Concurrency and parallelism, Trait objects, Async, Unsafe This section (More synta…

Update: as confirmed in the bug I logged, this was fixed in Firefox 123! See also: Keep your Indexed DB keys and values small if you want good performance! and Don’t store arrays of numbers in Indexed DB – use base64 instead. We had performance problem…

Following on from Keep your Indexed DB keys and values small if you want good performance!, here is another thing I’ve learned about Indexed DB performance (in July 2024): Update: Thanks to richvdh, we now know UInt8Array is much better than base64! If…

What a String is in Rust, and how they differ from &str. Strings are resizeable arrays of bytes that are guaranteed to be in UTF-8 format. &strs are references to chunks of bytes that are also guaranteed to be in UTF-8 format. If you want to le…